Centering theory (CT) is a theory of discourse structure which models the interaction of cohesion and salience in the internal organisation of a text. Centering has been mostly discussed from the point of view of interpretation rather than generation, and research has tended to concentrate on problems of anaphora resolution. This talk will examine how centering could fit into the generation task, separating out components of the theory which are concerned with planning and realisation. We argue that it is a mistake to define a total ordering on the transitions continue, retain, shift and that they are in fact epiphenomenal; a partial ordering emerges from the interaction between cohesion (maintaining the same center) and salience (realising the center as Subject). CT has generally been neglected by NLG practitioners, possibly because it appears to assume that the center is determined according to feedback from the surface grammar to text planning, but we argue that this is an artefactual problem which can be eliminated on an appropriate interpretation of the CT rules.
This talk is based on Kibble, 1999, Cb or not Cb? Centering theory applied to NLG, a paper to be presented at ACL workshop on Discourse and Reference Structure, University of Maryland, June 1999.